When North Carolina legislators made moves this month to establish an official state religion, observers might have gotten the impression that Americans were harkening back to an era of intolerance. That's not true. The line between Christian and Jew or Protestant and Catholic is now a mere shadow of the line between Red America and Blue America.

Religious tolerance is at an all time high. One sign is the fact that interfaith marriages are at record levels.

I commissioned a nationally representative survey of about 2,500 people in 2010 and found that nearly 45% of marriages in the decade before were interfaith matches. That's more than double the 20% rate for couples married before the 1960s.

Intermarriage is found across faiths. The 2001 American Religious Identification Survey reported that 39% of Buddhists, 27% of Jews, 23% of Catholics, 21% of Muslims, 18% of Baptists and 12% of Mormons were married to a spouse of a different faith. Regardless of income level, education, or geography, interfaith marriage among Americans is on the rise.

But the same is not true for marriages across political parties. Among all married people, 36% have interfaith marriages, but my survey by the polling firm YouGov found that only 18% have a spouse with a different political affiliation.

During the election last fall, when politics were heating up, The New York Times reported on Paul Ryan's unusual cross-partisan marriage, while advice columnists were bombarded with letters about whether relationships between Democrats and Republicans can work out. Sherry Amatenstein, the dating columnist for More magazine, wrote, "Can't blue and red singles ever all just get along? In Obama-speak: Yes we can."

Perhaps we can. But we don't.

A January 2008 survey by the social networking site Engage.com "found that 85% of those polled are open to dating someone outside their party." At the same time, more married Americans believe it is "very important" for a happy marriage that spouses share the same religion than say they should have the same race or the same political views.

Political map

Why do we say a common religion is more important than a common political outlook but then go out and marry across religions more than across political parties? There are some obvious reasons. We are more likely to live near, go to school with and work with people of a similar political bent, so they are easier to ask on a date. (The famous red-state/blue-state election map certainly leads to this conclusion.)

But the main reason could lie in the way we date and how an increasingly religiously unaffiliated society thinks about religious belief.

The road to marriage is long these days. The average age of first marriage is 27 for women and 29 for men. Couples often spend years living together before tying the knot. Young adults want to find out how they will interact when they're together all the time, what it will be like to share chores and whether they can tolerate each other's families.

Religion plays less of a role. Partially, it is a factor of meeting mates in our 20s and 30s, our most secular time in life, when we often stop going to church or synagogue. Young adults compartmentalize the religious aspects of their lives, considering religion an individual pursuit.

The modern emphasis on personal spirituality over organized religion might suggest that your beliefs are between you and God. Checking in on a partner's beliefs seems too personal. More than half of interfaith couples who intend to have kids don't even bother to talk about how they will be raised religiously.

Which makes you wonder what they do talk about. It is hard to imagine that young adults compartmentalize politics before tying the knot. Most of us have a better idea of what our friends and family think about President Obama than about God. Sitting around watching Jon Stewart at night, politics has to come up in a way that religion doesn't.

But are varying views on tax rates or foreign policy really as significant as varying views on where we go when we die? Of course, political views can encompass more serious disagreements about the permissibility of abortion or how wealth should be distributed. Indeed, the point is not that serious political differences can or should be ignored. It's that religious differences often are.

Naomi Schaefer Riley is the author of 'Til Faith Do Us Part: How Interfaith Marriage Is Transforming America.

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